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Thymosin Alpha-1

Evidence grade: Human trials

An immune-modulating thymic peptide approved in dozens of countries, with the most substantial regulatory footprint of anything on this site.

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KPV

Evidence grade: Animal studies only

The smallest active fragment of alpha-MSH, studied as an anti-inflammatory without the pigmentation effects of the parent hormone.

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1 cited source1 human studyReviewed 1 Jun 2026
1 cited source1 human studyReviewed 1 Jun 2026

At a glance

At a glance compared across Thymosin Alpha-1, KPV
AttributeThymosin Alpha-1KPV
Primary useImmune & recoveryImmune & recovery
Evidence gradediffersHuman trialsAnimal studies only
Human dataYes — see citationsYes — see citations
Cited sources1 source · 1 human1 source · 1 human
In one sentenceAn immune-modulating thymic peptide approved in dozens of countries, with the most substantial regulatory footprint of anything on this site.The smallest active fragment of alpha-MSH, studied as an anti-inflammatory without the pigmentation effects of the parent hormone.

Mechanism

Mechanism compared across Thymosin Alpha-1, KPV
AttributeThymosin Alpha-1KPV
How it is thought to workThymosin alpha-1 is produced by the thymus and modulates T-cell maturation and dendritic cell function. Rather than stimulating the immune system indiscriminately, it appears to restore balance — which is why it has been studied both in immune deficiency and in conditions with excessive inflammation.KPV is the three-amino-acid C-terminal tail of alpha-melanocyte-stimulating hormone, which retains anti-inflammatory activity while dropping the melanocortin receptor binding responsible for pigmentation. It inhibits NF-κB signalling and downstream pro-inflammatory cytokine production, and it appears to be taken up directly by intestinal epithelial cells.
What the research reports
  • Approved in over 30 countries for hepatitis B, hepatitis C and as a vaccine adjuvant
  • Randomised trials in sepsis reporting mortality benefit
  • Studied extensively during COVID-19 for immune restoration
  • Reduced inflammatory markers in several trial settings
  • Reduced colonic inflammation in mouse models of colitis
  • NF-κB pathway inhibition
  • Antimicrobial activity in vitro
  • Wound healing effects in animal models
What it is NOT shown to do
  • Not FDA-approved in the United States
  • No cognitive or mood endpoint trials
  • The mental-health link is inferential, via inflammation
  • No human trials
  • No mood or cognition data

Dosing & pharmacology

Dosing & pharmacology compared across Thymosin Alpha-1, KPV
AttributeThymosin Alpha-1KPV
Routes studieddiffersSubcutaneousOral, Subcutaneous, Topical
Half-lifediffersRoughly 2 hours; immune effects persist far longerShort; oral use targets local gut action rather than systemic exposure
Dose referenceClinical protocols commonly use 1.6 mg subcutaneously twice weekly, under medical supervision.Community protocols commonly cite 200–500 mcg/day. Not trial-derived.
Typical study cyclediffersClinical courses run weeks to months depending on indicationCommunity protocols run 4–8 weeks

Chemistry & handling

Chemistry & handling compared across Thymosin Alpha-1, KPV
AttributeThymosin Alpha-1KPV
Sequence28 residues, N-terminally acetylated: Ac-SDAAVDTSSEITTKDLKEKKEVVEEAENLys-Pro-Val (the C-terminal tripeptide of α-MSH)
Molecular formuladiffersC129H215N33O55C16H30N4O4
Molecular weightdiffers3108.3 g/mol342.4 g/mol
CAS numberdiffers62304-98-767727-97-3
Storage (reconstituted)2–8 °C, typically used within 2–4 weeks2–8 °C, typically used within 2–4 weeks

Risk

Risk compared across Thymosin Alpha-1, KPV
AttributeThymosin Alpha-1KPV
Reported side effects
  • Injection-site reaction
  • Transient flu-like symptoms
  • Sparse data; generally reported as well tolerated
Contraindications
  • Immunosuppressed transplant recipients — immune modulation can threaten graft tolerance
  • Autoimmune disease without specialist oversight
  • Pregnancy and breastfeeding
  • Pregnancy and breastfeeding
  • Autoimmune disease without oversight

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